The invention pertains in general to high-voltage tolerant output drivers and more specifically to a high-voltage tolerant output driver for a switching regulator.
Advances in integrated circuit (IC) technology have led to higher levels of integration (i.e., density) and performance. Today's IC devices have more circuitry than ever and operate at much faster speeds. However, higher circuit densities have correspondingly increased the amount of power dissipated by these devices. IC density is often limited by the amount of power dissipated by the chip and the resulting heat produced.
In order to overcome these and other disadvantages associated with increased density, manufacturers have developed new processes to produce ICs that operate at lower voltage levels. Some common IC operating voltage levels include 5V+/−10%, 3.3V+/−10%, and 2.5V+/−10%. In using decreased voltage levels, manufacturers limit the adverse effects of power dissipation (e.g., heat), while continuing to allow for ever increasing IC densities.
Nevertheless, when a new, low-voltage IC process technology emerges, it is often desirable for the new technology to be able to operate with existing high-voltage levels. IC process technologies, and their respective operating voltages, are often defined by the gate-oxide breakdown voltage between the terminals of a device (e.g., a transistor) implemented using the particular process technology. Consequently, a potential problem with interfacing circuitry implemented in a low-voltage process technology with a voltage that exceeds device limits is that, one or more devices implemented in the low-voltage process may experience damage, either temporary or permanent, that can hinder the circuit's ability to perform its desired function.
A switching regulator, implemented at least partially in a low-voltage IC process technology, is one example circuit where it is often desirable to operate with existing high-voltage levels. For example, a switching regulator implemented in a 2.5 V IC process technology can typically tolerate voltages as high as 2.75 V. However, the switching regulator may be required to regulate an input voltage that may exceed voltages of 2.75 V. Conventional implementations of the switching regulator and, in particular, the output driver circuitry of the switching regulator, cannot tolerate voltages higher than 2.75 V without experiencing problems. As such, conventional output driver circuitry used in a switching regulator cannot regulate voltages that exceed the IC process technology limits, which in this example is 2.75 V.
It is therefore desirable to provide a high-voltage tolerant output driver for use in a switching regulator circuit, implemented in low-voltage IC process technology. Further aspects and advantages of this invention will become apparent from the detailed description that follows.
The present invention will be described with reference to the accompanying drawings. The drawing in which an element first appears is typically indicated by the leftmost digit(s) in the corresponding reference number.